Broad objectives are to examine direct and mediating effects of life stressors and perceived stress on biological systems associated with vulnerability to alcoholism. Both stress and family history have been shown to be strong predictors of risk for alcoholism, but mechanisms remain unclear. SPECIFIC AIMS: 1) To determine whether stress is associated with HPA axis function, DA neurotransmission, or subjective alcohol liking, 2) To examine relationships between life stressors, perceived stress, and family history of alcoholism, 3) To determine whether the relationship between family history and HPA axis function or DA neurotransmission is influenced by stress. METHODS: 100 M, F 21-26 year-old social drinkers will be hospitalized for 11 days on the GCRC. Information about family history, psychological symptoms, stress symptomatology, and personality will be obtained. Each subject will undergo 3 PET scans to assess DA neurotransmission. A psychological stress test will be used to evaluate HPA axis function. Individual differences in alcohol sensitivity will be evaluated with alcohol challenges. We hypothesize that pre-existing stress will be positively associated with DA release, HPA axis activity, and alcohol liking. Findings could improve preventative care of high-risk nonalcoholics and treatment of alcohol dependent persons by helping to clarify biological processes involved in the relationship between stress reactivity and alcohol reinforcement.